Sulfuric acid plants are well known in the art and typically operate with relatively high efficiency. However, most sulfuric acid plants generate a tail gas that has a substantial concentration of SO2 and the tail gas is therefore generally not acceptable for venting into the atmosphere. To reduce SO2 emissions, various processes are known. For example, tail gas can be subjected to a continuous amine absorption process as described in U.S. Pat. Nos. 3,904,735 and 7,776,296. These and all other extrinsic materials presented herein are incorporated by reference in their entirety. Furthermore, where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
A typical sulfuric acid plant is exemplarily depicted in Prior Art FIG. 1 where a conventional downstream amine absorber unit removes SO2 from the reactor offgas in a continuous fashion. More specifically, an offgas from a sulfur burner is fed to a sulfuric acid plant, and the catalytic reactor produces sulfuric acid and a tail gas rich in sulfur species (and particularly SO2). The tail gas is typically fed to an amine absorber that operates with a lean solvent to so produce a rich solvent that is subsequently regenerated in a SO2 stripper. The so removed SO2 is recycled to the front end of the plant while the lean solvent is fed back to the amine absorber. Thus, the tail gas can be treated to relatively low levels of SO2. While such configurations often achieve satisfactory results during normal operating conditions, SO2 removal is not achieved when the continuous amine process is interrupted.
To avoid unintended SO2 release into the atmosphere, most plant operators choose one of two common options. In one option, an additional continuous amine absorption system is implemented as a back-up system and only started upon failure of the first system. While such back-up option generally has a large capacity to remove SO2, significant capital cost and low SO2 removal capacity during start-up is commonly encountered. Alternatively, two full-sized sulfuric acid plants can be run in parallel at half capacity. Thus, when the SO2 removal unit of one plant is down, SO2 removal can be achieved by the SO2 removal unit of the other plant. While such option advantageously overcomes difficulties associated with start-up conditions, the substantial cost of installation and operation is often a significant drawback.
Therefore, even though several options for SO2 removal from sulfuric acid plants are known in the art, there is still a need to provide improved back-up systems and methods for sulfur plants.